1. Field of Invention
The present invention relates to a method of printing an indication of defective printing that prints a defective printing mark indicating that the printer did not print normally on a print medium, e.g. paper, when printing occurs because ink droplets are not discharged normally from the ink nozzles of an inkjet head. The present invention also relates to an inkjet printer and a printer driver, and to a defective printing notification method.
2. Description of Related Art
Serial inkjet printers print by discharging ink droplets from the ink nozzles of an inkjet head so that the ink droplets land at the desired position on recording paper that is conveyed perpendicularly to a main scanning direction while moving the inkjet head mounted on a carriage in the main scanning direction.
Inkjet printers that use a line inkjet head print by conveying recording paper positioned opposite a stationary inkjet head while depositing ink droplets at desired positions on the paper.
If an ink nozzle becomes clogged by, for example, a bubble left in the ink nozzle, or if foreign matter is left on the nozzle surface of the inkjet head, the ink droplets may be deposited at a different position than the desired position, or ink droplets may not be discharged, and a printing defect characterized by unprinted or missing dots occurs.
When printing labels that are applied to medical products used in medical facilities, for example, high quality printing that is free of this missing dot problem is essential to prevent treatment errors caused by reading errors. High quality printing free of missing dots is also required when printing two-dimensional symbols such as QR Code symbols to avoid errors when read by a code reader. To avoid such problems caused by missing dots, Japanese Unexamined Patent Appl. Pub. JP-A-2003-118133 discloses a serial inkjet printer that can detect whether or not ink droplets are discharged normally from each of the ink nozzles and can appropriately execute a nozzle recovery operation. More specifically, this serial inkjet printer detects whether or not ink droplets are discharged correctly from each if the plural ink nozzles before printing such items. If ink droplets are not discharged correctly, the printer executes a nozzle recovery operation such as vacuuming ink and bubbles from each of the ink nozzles, or wiping the nozzle surface of the inkjet head, to restore the nozzles to the normal working condition.
Even if a nozzle recovery process is executed before printing starts, ink droplets may cease being discharged correctly from one or more ink nozzles while printing the print data on the recording paper.
Furthermore, because it can be difficult to identify from the printout whether there are missing dots, printouts having missing dots can be mistakenly read as though they had been printed correctly. When a printout with missing dots is used, the printed content may be read incorrectly depending on the type of printout, and the printed output becomes less reliable.